1. Field of the Invention
The present invention relates to a communication system for communicating with an external telephone apparatus and the like using an analog or digital communication line, and a communication control apparatus preferably used for the communication system.
2. Description of the Related Art
Unlike the conventional analog telephone technology, the network telephone technology for communications performed by sending/receiving speech packets via a network such as the Internet is advantageous, for example, in that long distance communications can be performed at a low rate or a fixed charge, and therefore is expected to be commonly used and developed from now on. For example, charges for communications over network telephones are constituted only by calling fees and access fees to an access point provided by a provider as in the case of the conventional Internet connection, so that communications can be performed at low rates, irrespective of the distance from a person to be communicated with.
However, the network telephone technology is still under development, and is incapable of providing all services that have been established in the conventional analog telephone technology. In particular, for an emergency call to police stations or for an ambulance, the location of a caller should be identified on the receiving side, and therefore the network telephone, which is incapable of identifying the location of a caller, cannot be used for emergency calls. Therefore, when using the network telephone, it is necessary to establish a configuration in which both the network telephone technology and the analog telephone technology can be used.
In order to connect to a plurality of communication lines (e.g., the Internet and telephone lines) simultaneously for the purpose of using both the network telephone technology and the analog telephone technology, it is necessary to control communications between a plurality of telephone apparatuses and a plurality of communication lines by introducing a communication control apparatus such as a gateway apparatus. Furthermore, the following techniques are published: a technique in which a gateway apparatus detects a particular operation (e.g., determination by a dial number or a dedicated button) input from a telephone apparatus and selects an appropriate communication line to perform communications when utilizing a service available only via a particular communication line; and a technique of disconnecting a communication line that is being used by another telephone apparatus to have the line available for an emergency call when making the emergency call through a telephone apparatus.
The switchboard disclosed in Japanese Unexamined Patent Publication JP-A 2000-184411 (2000) selects a particular network from a plurality of connectable networks including the Internet based on a dialed number or an operation. Thus, the networks to be connected can be switched by a simple operation.
In the public base station of a communication system disclosed in Japanese Unexamined Patent Publication JP-A 11-215238 (1999), when a line is busy, a particular number is called so that a portable terminal using the line for communications performs an urging operation for urging the user to finish the communications. The public base station, which has received a signal indicating the end of the call from the portable terminal, disconnects the communications and establishes communications for the portable terminal that called the particular number. Thus, the busy state can be eliminated in a short time.
The key telephone apparatus disclosed in Japanese Unexamined Patent Publication JP-A 63-45995 (1988) disconnects communications through key telephone terminals, upon an input of an emergency contact command by control means, and performs paging to all of the terminals from the terminal that has transmitted the emergency contact command. Thus, it is possible to perform the paging to all of the terminals at the same time.
The telephone apparatus disclosed in Japanese Unexamined Patent Publication JP-A 7-240774 (1995) includes a parent apparatus having an emergency notification button and a cordless child apparatus. When the emergency notification button is pressed while the child apparatus is communicating, then a rumbling tone signal is transmitted from the host apparatus to the slave apparatus. This makes it possible that the slave apparatus can stop the communications immediately.
In addition, there is a standard referred to as HomePNA (Home Phoneline Networking Alliance). With this standard, both analog telephone signals and digital data signals can be transferred via an indoor telephone wire, so that communications over the conventional analog telephone and the network telephone can be performed with a single interface, and also apparatuses for this standard are on sale.
When making an emergency call to a police station or a fire station (for fire-fighting or an ambulance), using a telephone apparatus that detects an dialed number or an operation and selects an appropriate communication line from a plurality of connectable communication lines including the Internet communication line for communications such as the switchboard disclosed in JP-A 2000-184411, a gateway apparatus selects an analog telephone line from a plurality of communication lines based on an inputted telephone number to transmit signals for an emergency call. If the analog telephone line is in use by another telephone apparatus, then a process for disconnecting the communications over that telephone apparatus to make the analog telephone line available can be performed.
However, a user who was engaged in communications previously with the analog telephone line does not know the cause of the disconnection and has to perform an operation for calling back. Moreover, when the analog line is in use when calling back, then operations, for example, for searching an open line or using a digital line are also required. Furthermore, the user on the emergency call transmission side can know the cause for the disconnection easily because this user is relatively near the user who has transmitted signals for the emergency call. However, it is difficult for the other user who has been interrupted during his/her call to know the cause for the disconnection. Thus, the communication control process by the conventional gateway apparatus imposes a heavy burden on users after the disconnection of the communications and is significantly user-unfriendly.